The core component of the program project grant contains professional expertise and support personnel and functions that serve multiple projects. The following constituents make up this portion of the grant: 1) Overall administrative services, including the activities of an administrative assistant, a secretary, and the core leader. 2) Common elements of data collection and processing, including the activities of a data collection coordinator, editors, coders, and other research assistants. 3) Computer programming, including the activities of two programmers. 4) Nutritional support, including personnel involved in maintaining a food composition data bank. 5) Biostatistical support, including the activities of the senior biostatistician and the support biostatistician. 6) Consultant services, including ad hoc visits from scientists with expertise in areas related to the research. The activities Of the personnel in each of these core constituents are explained. In addition, the overall organization and management of the core is described, including performance standards and quality control procedures. The core contains activities that are difficult to allocate precisely to individual projects because of changing and unanticipated needs, and that are most efficiently utilized when there is flexibility in their distribution to individual projects. By sharing these resources from a common source, the goals of the program can be accomplished with a smaller, more efficient staff. Furthermore, members of the core have a commitment to the entire program project, which contributes to the integration of the overall effort.